0_Tutorial/Custom Cursor.html

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<h1>
Tutorial: Writing a custom HIView
</h1>
 
<h2>
D) Implementing support for custom cursor appearance
</h2>
 
<p>
The support for custom cursor appearance is done by handling the kEventControlTrackingAreaEntered and kEventControlTrackingAreaExited events.
</p>
 
<p>
As usual, we add those two events to the event list that we register in GetHICustomViewClass and we add the two very simple cases in the function Internal_HICustomViewHandler:
</p>
 
<div class="mycodebox"><pre>
case kEventControlTrackingAreaEntered:
   {
   // setting the cursor when we pass over our custom view
   SetThemeCursor(kThemeCountingUpHandCursor);
   break;
   }
 
case kEventControlTrackingAreaExited:
   {
   // resetting the cursor when we leave custom view
   SetThemeCursor(kThemeArrowCursor);
   break;
   }
</pre></div>
 
<p>
Of course, if you have multiple parts, you may grab the precise mouse location and key modifiers if any from the EventRef and determine which cursor should be used.
</p>
 
<p>
Since we want our custom HIView to have automatic cursor tracking when created, we need to adjust our kEventHIObjectInitialize event handler which now does something useful:
</p>
 
<div class="mycodebox"><pre>
case kEventHIObjectInitialize:
   {
   // always begin kEventHIObjectInitialize by calling through to the previous handler
   status = CallNextEventHandler(inHandlerCallRef, inEvent);
   require_noerr(status, InitializeExit);
   
   // if that succeeded, do our own initialization
   HIViewTrackingAreaRef trackRef;
   status = HIViewNewTrackingArea(myData->view, NULL, 0, &trackRef);
   require_noerr(status, InitializeExit);
 
InitializeExit:
   break;
   }
</pre></div>
 
<p>
We do not need to clean after ourselves in the kEventHIObjectDestruct event handler since the HIToolbox will automatically dispose any tracking area associated with your view when that view is destroyed.
</p>
 
<p>
In our example you will simply see:
</p>
 
<img src="../0_Tutorial/Picture%205.png" alt="" width="535" height="468">
 
<p>
You can test the custom HIView for this step by using the project located in the folder “5_Tracking_Area”.
</p>
 
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